Cells Can Sense and Respond to Mechanical Forces

The biological cell constitutes the basic unit of life and performs a large variety of functions through synthesis, sorting, storage, and transport of biomolecules; expression of genetic information; recognition, transmission, and transduction of signals; and converting different forms of energy [1]. Many of the cellular processes involve mechanical force, or deformation, at the cellular, subcellular, and molecular levels [2, 3]. For example, biomolecular motors and machines convert chemical energy into mechanical motion in performing their diverse range of functions [4, 5]. During cell migration, contractile forces must be generated within the cell in order for the cell body to move forward [6]. Adhesion of cells to an extracellular matrix (ECM) through focal adhesion complexes is sensitive to the stiffness of the substrate [7, 8]. All living cells on Earth are constantly under physical force (gravitational and other forms of force), and many normal and diseased conditions of cells are dependent on or regulated by their mechanical environment. Some cells, such as bone and endothelial cells, are subjected to specific forces as part of their “native” physiological environment. Some other cells, such as muscle and cochlear outer hair cells [9], perform a mechanical function by converting an electrical or chemical stimulus into a mechanical motion.